The term nickel alloy refers to a metal that has nickel as one of its primary elements. Some types of nickel alloys are referred to as superalloys because of their superior oxidation and creep resistance, allowing them to be used at temperatures of more than half their melting points. Nickel alloys can be machined and welded but tend to pose some processing difficulties, as some alloys will work harden during machining, and their high melting points can make them difficult to weld.